The static keyword and its various uses in C++

When static keyword is used, variable or data members or functions can not be modified again. It is allocated for the lifetime of program. Static functions can be called directly by using class name.

Static variables are initialized only once. Compiler persist the variable till the end of the program. Static variable can be defined inside or outside the function. They are local to the block. The default value of static variable is zero. The static variables are alive till the execution of the program.

The following is the syntax of static keyword.

static datatype variable_name = value; // Static variable
   static return_type function_name { // Static functions
   ...
}

Here,

datatype − The datatype of variable like int, char, float etc.

variable_name − This is the name of variable given by user.

value − Any value to initialize the variable. By default, it is zero.

return_type − The datatype of function to return the value.

function_name − Any name to the function.

The following is an example of static keyword.

Example

 Live Demo

#include <bits/stdc++.h>
using namespace std;
class Base {
   public : static int val;
   static int func(int a) {
      cout << "\nStatic member function is called";
      cout << "\nThe value of a : " << a;
   }
};
int Base::val=28;
int main() {
   Base b;
   Base::func(8);
   cout << "\nThe static variable value : " << b.val;
   return 0;
}

Output

Static member function is called
The value of a : 8
The static variable value : 28

In the above program, a static variable is declared. A static function is defined in the class Base as shown below −

public : static int val;
static int func(int a) {
   cout << "\nStatic member function called";
   cout << "\nThe value of a : " << a;
}

After the class and before main(), the static variable is initialized as follows.

int Base::val=28;

In the function main(), object of Base class is created and static variable is called. The static function is also called without using object of Base class.

Base b;
Base::func(8);
cout << "\nThe static variable value : " << b.val;